1. Field of the Invention
The present invention relates to an electronic circuit unit suitable for use in portable telephones or the like, and a method of manufacturing the same.
2. Description of the Related Art
The conventional electronic circuit unit will be explained with reference to FIG. 6 and FIG. 7. A circuit board 21 has a plurality of cutout sections 21b formed on the end faces 21a thereof and conductive patterns 22 formed on the upper side thereof, and on the cutout sections 21b are formed end-face electrodes 23 that are connected to the conductive patterns 22.
Further, electronic components (not illustrated) such as resistors, capacitors, and the like are mounted on the circuit board 21 in a state that the electronic components are connected to the conductive patterns 22, and thus an electronic circuit unit 24 is configured with the one circuit board 21.
Further, as shown in FIG. 7, a printed board 25 serving as a mother board includes conductive wiring patterns 26 formed on the surface thereof and a plurality of lands 27 for soldering, which are formed on the ends of the conductive wiring patterns 26.
And, as shown in FIG. 7, the electronic circuit unit 24 is mounted on the printed board 25 as the mother board of the portable telephone or the like, and the end-face electrodes 23 provided on the circuit board 21 of the electronic circuit unit 24 are bonded onto the lands 27 provided on the printed board 25 through solders 28, whereby the electronic circuit unit 24 is connected to the conductive wiring patterns 26 on the printed board 25, and at the same time it is mounted to the printed board 25.
With regard to the method for mounting the electronic circuit unit 24 to the printed board 25, first, cream solders (not illustrated) are applied on the lands 27, as shown in FIG. 7.
Next, the electronic circuit unit 24 is mounted on the printed board 25 in a state that the end face electrodes 23 are located on the cream solder, and the printed board 25 having the electronic circuit unit 24 mounted in this state is carried into a heating furnace, whereby the cream solder is melted to bond the end face electrodes 23 to the lands 27 through the solder 28.
However, in these mounting structure and method, since the soldering is made with the cream solder applied on the lands 27 on the printed board 25, this method is difficult to make sufficient buildup of the solders 28, and also difficult to secure good wettability of the solders 28 to the end-face electrodes 23.
Further, when the circuit board 21 is warped due to a temperature variation, aged deterioration, or the like, both ends of the circuit board 21 are lifted up as shown in FIG. 7; and especially in such a warped circuit board 21, the cream solder is difficult to wet the end face electrodes 23.
Thus, in the conventional electronic circuit unit, since the soldering is made with the cream solder applied on the lands 27 on the printed board 25, sufficient buildup of the solder 28 is difficult to be made, so that good wettability of the solders 28 to the end face electrodes 23 cannot be achieved, which is a problem to be solved.
Further, with regard to the circuit board 21 having a warp, the wettability of the cream solder to the end face electrodes 23 becomes still worse, which is another problem.
In a first embodiment to solve the foregoing problem, the electronic circuit unit of the present invention assumes a configuration containing a circuit board having conductive patterns on one face thereof and conductive lands connected to the conductive patterns on the other face thereof, in which electronic components such as resistors and capacitors, etc., connected to the conductive patterns are mounted on one face of the circuit board, a solder resist is provided on the other face of the circuit board, the lands are made up with broad width lands exposed from the solder resist and one or more thin width lands tied with the broad width lands in a state of being exposed from the solder resist, and the broad width lands have solder buildup formed thereon.
in a second embodiment to solve the problem, the electronic circuit unit of the present invention takes on circular broad width lands.
Further, as a third embodiment to solve the problem, the electronic circuit unit of the present invention takes on a configuration such that the broad width lands are formed near the end faces of the circuit board.
Further, as a forth embodiment to solve the problem, in the method of manufacturing an electronic circuit unit of the present invention, the electronic circuit unit is configured with a circuit board having conductive patterns on one face thereof and conductive lands connected to the conductive patterns on the other face thereof, in which electronic components such as resistors and capacitors, etc., connected to the conductive patterns are mounted on the one face of the circuit board, a solder resist is provided on the other face of the circuit board, and the lands are made up with broad width lands exposed from the solder resist and one or more thin width lands tied with the broad width lands in a state of being exposed from the solder resist. With this configuration, the method of the present invention comprises the steps of: applying cream solder on the broad width lands and the solder resist surrounding thereof, and on the thin width lands and the solder resist surrounding thereof, thereafter, at least heating the cream solder, and forming solder buildups on the broad width lands.
Further, as a fifth embodiment to solve the problem, the method of the present invention takes on circular broad width lands.
Further,as a sixth embodiment to solve the problem, the method of the present invention takes on a configuration such that the broad width lands are formed near the end faces of the circuit board.